Showing papers on "Transport phenomena published in 2022"

Quantum mechanical modeling of magnon-phonon scattering heat transport across three-dimensional ferromagnetic/nonmagnetic interfaces

Abstract: Magnon-phonon scattering (MPS) has attracted widespread attention in quantum heat/spin transport across the ferromagnetic/nonmagnetic (F/N) interfaces, with the rapid progress of experiments on spin caloritronics in recent years. However, the lack of theoretical methods, accounting for the MPS rigorously, has seriously hindered investigations on the quantum heat transport in magnetic nanostructures with broken translational symmetry, such as F/N interfaces. In this paper, we propose a theoretical formalism of the nonequilibrium Green function to incorporate the MPS into the quantum heat transport for three-dimensional ferromagnetic nanostructures, rigorously, through a diagrammatic perturbation analysis. A computational scheme is developed for the first-principles simulation of quantum heat transport in practical magnetic nanostructures, and a generalized formalism of heat flow is presented for the analysis of the elastic and inelastic process of heat transport. A thermal rectification driven by MPS is observed in the numerical simulation of heat transport across the F/N interface based on the ${\text{CrI}}_{3}$ monolayer, which is consistent with recent studies. In this paper, we open the gate to first-principles investigations of quantum heat transport in magnetic nanostructures and pave the way for the theoretical design of magnetic thermal nanodevices.

Spectral Numerical Study of Entropy Generation in Magneto-Convective Viscoelastic Biofluid Flow Through Poro-Elastic Media With Thermal Radiation and Buoyancy Effects

Abstract: Electromagnetic high-temperature therapy is popular in medical engineering treatments for various diseases include tissue damage ablation repair, hyperthermia and oncological illness diagnosis. The simulation of transport phenomena in such applications requires multi-physical models featuring magnetohydrodynamics, biorheology, heat transfer and deformable porous media. Motivated by investigating the fluid dynamics and thermodynamic optimization of such processes, in the present article a mathematical model is developed to study the combined influence of thermal buoyancy, magnetic field and thermal radiation on the entropy generation, momentum and heat transfer characteristics in electrically-conducting viscoelastic biofluid flow through a vertical deformable porous medium. Jefferys elastic-viscous model is deployed to simulate non-Newtonian characteristics of the biofluid. “It is assumed that heat is generated within the fluid by both viscous and Darcy (porous matrix) dissipations. The governing equations for fluid velocity, solid displacement and temperature are formulated in a Cartesian coordinate system. The boundary value problem is normalized with appropriate transformations. The non-dimensional biofluid velocity, solid displacement and temperature equations with appropriate boundary conditions are solved computationally using a spectral method. Verification of accuracy is conducted via monitoring residuals of the solutions. Validation of solutions with Runge-Kutta shooting quadrature is included. The effects of Jeffrey viscoelastic parameter, viscous drag parameter, magnetic field parameter, radiation parameter and buoyancy parameter on flow velocity, solid displacement, temperature and entropy generation are depicted graphically and interpreted at length. Increasing magnetic field and drag parameters are found to reduce the field velocity, solid displacement, temperature and entropy production. Higher magnitudes of thermal radiation parameter retard the flow and decrease Nusselt number whereas they elevate solid displacement. Entropy production is enhanced with an increase in buoyancy parameter and volume fraction of the fluid. The novelty of the work is the simulatenous inclusion of multiple thermophysical phenomena and the consideration of thermodynamic optimization in coupled thermal/fluid/elastic media. The computations provide an insight into multi-physical transport in electromagnetic radiative tissue ablation therapy and a good benchmark for more advanced simulations.

A Closer Look: High-Resolution Pore-Scale Simulations of Solute Transport and Mixing Through Porous Media Columns

Abstract: Mixing is pivotal to conservative and reactive transport behaviors in porous media. Methods for investigating mixing processes include mathematical models, laboratory experiments and numerical simulations. The latter have been historically limited by the extreme computational resources needed for solving flow and transport at the microscopic scale within the complex pore structure of a three-dimensional porous medium, while dealing with a sufficiently large domain in order to generate meaningful emergent continuum-scale observables. We present the results of such a set of virtual column experiments, which have been conducted by taking advantage of modern high-performance computing infrastructure and Computational Fluid Dynamics software capable of massively parallel simulations. The computational approach has important advantages such as full control over the experimental conditions as well as high spatial and temporal resolution of measurements. Hydrodynamic dispersion results agree with the empirical and theoretical literature and link dispersivity to median grain size, while elucidating the impact of grain size variability on the critical Péclet number. Reactive transport results also indicate that the relative degree of incomplete mixing is related to the granular material’s mean hydraulic radius and not directly to the median grain size. When compared to a well-known laboratory experiment with similar configuration, less incomplete mixing is observed in our simulations. We offer a partial explanation for this discrepancy, by showing how an apparent nonlinear absorbance–concentration relationship may induce laboratory measurement error in the presence of local concentration fluctuations.

Modelling Sorption and Transport of Gases in Polymeric Membranes across Different Scales: A Review

Abstract: Professor Giulio C. Sarti has provided outstanding contributions to the modelling of fluid sorption and transport in polymeric materials, with a special eye on industrial applications such as membrane separation, due to his Chemical Engineering background. He was the co-creator of innovative theories such as the Non-Equilibrium Theory for Glassy Polymers (NET-GP), a flexible tool to estimate the solubility of pure and mixed fluids in a wide range of polymers, and of the Standard Transport Model (STM) for estimating membrane permeability and selectivity. In this review, inspired by his rigorous and original approach to representing membrane fundamentals, we provide an overview of the most significant and up-to-date modeling tools available to estimate the main properties governing polymeric membranes in fluid separation, namely solubility and diffusivity. The paper is not meant to be comprehensive, but it focuses on those contributions that are most relevant or that show the potential to be relevant in the future. We do not restrict our view to the field of macroscopic modelling, which was the main playground of professor Sarti, but also devote our attention to Molecular and Multiscale Hierarchical Modeling. This work proposes a critical evaluation of the different approaches considered, along with their limitations and potentiality.

Hydrodynamics of charged two-dimensional Dirac systems. I. Thermoelectric transport

Abstract: In this paper we study thermoelectric transport in interacting two-dimensional Dirac-type systems using a phenomenological Boltzmann approach. We consider a setup that can accommodate electrons, holes, and collective modes. In the first part of the paper we consider the electron-hole hydrodynamics, a model that is popular in the context of graphene, and its transport properties. In a second part, we propose a unique type of hydrodynamics. In that setup, the ``fluid'' consists of electrons, holes, and plasmons. We study its transport properties, especially the thermoelectric behavior. The results of this part can also be adapted to the study of a fluid consisting of electrons and phonons. This paper is accompanied by a technical paper [K. Pongsangangan et al., Phys. Rev. B 106, 205127 (2022)], in which we give a detailed derivation of the Boltzmann equations and the encoded conservation laws.

Numerical modeling of 2D hygro-thermal transport in unsaturated concrete with capillary suction

Abstract: In this study, the importance of capillary suction was emphasized through its implementation in a hygrothermal transport model used to predict water transport in ordinary concrete. In the model, heat transfer is described by the classical Fourier equation. In addition, the homogeneous vapor diffusion is modeled using a gradient-driven Fick's law, and the local kinematics of the liquid capillary flow are illustrated by a pressure-driven Darcy's law. Mathematical operations were performed to obtain a combined governing equation for water transport, but with different transport coefficient expressions under different circumstances. The complete hygrothermal transport model was discretized in a 2D finite element program (TransChlor2D) and solved using an explicit and one-way coupling scheme. Experimental methods and analytical formulas were used to assess the hygrothermal transport parameters, and the model was validated with various durability tests, demonstrating its ability to capture the impact of capillary flow on water content profiles.

Fundamental Understanding of Heat and Mass Transfer Processes for Physics-Informed Machine Learning-Based Drying Modelling

Abstract: Drying is a complex process of simultaneous heat, mass, and momentum transport phenomena with continuous phase changes. Numerical modelling is one of the most effective tools to mechanistically express the different physics of drying processes for accurately predicting the drying kinetics and understanding the morphological changes during drying. However, the mathematical modelling of drying processes is complex and computationally very expensive due to multiphysics and the multiscale nature of heat and mass transfer during drying. Physics-informed machine learning (PIML)-based modelling has the potential to overcome these drawbacks and could be an exciting new addition to drying research for describing drying processes by embedding fundamental transport laws and constraints in machine learning models. To develop such a novel PIML-based model for drying applications, it is necessary to have a fundamental understanding of heat, mass, and momentum transfer processes and their mathematical formulation of drying processes, in addition to data-driven modelling knowledge. Based on a comprehensive literature review, this paper presents two types of information: fundamental physics-based information about drying processes and data-driven modelling strategies to develop PIML-based models for drying applications. The current status of physics-based models and PIML-based models and their limitations are discussed. A sample PIML-based modelling framework for drying application is presented. Finally, the challenges of addressing simultaneous heat, mass, and momentum transport phenomena in PIML modelling for optimizing the drying process are presented at the end of this paper. It is expected that the information in this manuscript will be beneficial for further advancing the field.

Numerical modeling of 2D hygro-thermal transport in unsaturated concrete with capillary suction

Abstract: In this study, the importance of capillary suction was emphasized through its implementation in a hygrothermal transport model used to predict water transport in ordinary concrete. In the model, heat transfer is described by the classical Fourier equation. In addition, the homogeneous vapor diffusion is modeled using a gradient-driven Fick's law, and the local kinematics of the liquid capillary flow are illustrated by a pressure-driven Darcy's law. Mathematical operations were performed to obtain a combined governing equation for water transport, but with different transport coefficient expressions under different circumstances. The complete hygrothermal transport model was discretized in a 2D finite element program (TransChlor2D) and solved using an explicit and one-way coupling scheme. Experimental methods and analytical formulas were used to assess the hygrothermal transport parameters, and the model was validated with various durability tests, demonstrating its ability to capture the impact of capillary flow on water content profiles.

Transport Phenomena and Cell Overpotentials in Redox Flow Batteries

Abstract: Redox flow batteries are a promising technological option for large-scale energy storage, but their deployment is hampered by suboptimal performance and elevated costs. The reactor performance is determined by the mass, charge, momentum, and heat transport rates coupled with electrochemical reactions. Understanding, measuring, and simulating these metrics is thus necessary for device optimization. In this chapter, we first describe the main transport mechanisms and cell overpotentials relevant to flow batteries with a focus on single cells representative of individual units in a stack. Then, we critically review some experimental methods, including bulk and locally resolved diagnostics, which enable determination of cell overpotentials. Finally, we briefly describe the most promising modeling approaches. Our goal is to provide students and scientists with the fundamental guiding principles of transport phenomena and cell overpotentials that can be leveraged to design advanced materials and reactor architectures with enhanced performance.

Transport phenomena in complex systems (part 2)

Abstract: This theme issue, in two parts, continues research studies of transport phenomena in complex media published in the first part (Alexandrov & Zubarev 2021 Phil. Trans. R. Soc. A 379, 20200301. (doi:10.1098/rsta.2020.0301)). The issue is concerned with theoretical, numerical and experimental investigations of nonlinear transport phenomena in heterogeneous and metastable materials of different nature, including biological systems. The papers are devoted to the new effects arising in such systems (e.g. pattern and microstructure formation in materials, impacts of external processes on their properties and evolution and so on). State-of-the-art methods of numerical simulations, stochastic analysis, nonlinear physics and experimental studies are presented in the collection of issue papers. This article is part of the theme issue ‘Transport phenomena in complex systems (part 2)’.

Flux-based modeling of heat and mass transfer in multicomponent systems

Abstract: In the present work, the macroscopic governing equations governing the heat and mass transfer for a general multicomponent system are derived via a systematic nonequilibrium thermodynamics framework. In contrast to previous approaches, the relative (with respect to the mass average velocity) component mass fluxes (relative species momenta) and the heat flux are treated explicitly, in complete analogy with the momentum flux. The framework followed here, in addition to allowing for the description of relaxation phenomena in heat and mass transfer, establishes to the fullest the analogy between all transport processes, momentum, heat, and mass transfer, toward which R. B. Bird contributed so much with his work. The inclusion of heat flux-based momentum as an additional variable allows for the description of relaxation phenomena in heat transfer as well as of mixed (Soret and Dufour) effects, coupling heat and mass transfer. The resulting models are Galilean invariant, thereby resolving a conundrum in the field, and always respect the second law of thermodynamics, for appropriate selection of transport parameters. The general flux-based dynamic equations reduce to the traditional transport equations in the limit when mass species and heat relaxation effects are negligible and are fully consistent with the equations established from the application of kinetic theory in the limit of dilute gases. As an added benefit, for the particular example case of hyperbolic diffusion we illustrate the application of the proposed models as a method to allow the use of powerful numerical solvers normally not available for solving mass transfer models more generally.

Chemical transformations and transport phenomena at interfaces

Abstract: Interfaces, the boundary that separates two or more chemical compositions and/or phases of matter, alters basic chemical and physical properties including the thermodynamics of selectivity, transition states, and pathways of chemical reactions, nucleation events and phase growth, and kinetic barriers and mechanisms for mass transport and heat transport. While progress has been made in advancing more interface‐sensitive experimental approaches, their interpretation requires new theoretical methods and models that in turn can further elaborate on the microscopic physics that make interfacial chemistry so unique compared to the bulk phase. In this review, we describe some of the most recent theoretical efforts in modeling interfaces, and what has been learned about the transport and chemical transformations that occur at the air–liquid and solid–liquid interfaces.

Fundamentals and Transport Properties of Nanofluids

Abstract: Nanofluids are an emerging class of heat transfer fluids that are engineered by dispersing nanoparticles in conventional fluids. They represent a promising, multidisciplinary field that has evolved over the past two decades to provide enhanced thermal features, as well as manifold applications in thermal management, energy, transportation, MEMs and biomedical fields. Fundamentals and Transport Properties of Nanofluids addresses a broad range of fundamental and applied research on nanofluids, from their preparation, stability, and thermal and rheological properties to performance characterization and advanced applications. It covers combined theoretical, experimental and numerical research to elucidate underlying mechanisms of thermal transport in nanofluids. Edited and contributed to by leading academics in thermofluids and allied fields, this book is a must have for those working in chemical, materials and mechanical engineering, nanoscience, soft matter physics and chemistry.

Transport phenomena in gas membrane separations

Abstract: Membrane separation technology is used in a wide range of gas-separation applications and is now regarded as a cutting-edge separation technology for industrial applications. Membranes have the highest potential for gas separation. In the gas processing sector, a high degree of permeability combined with high selectivity of a particular gaseous species ensures outstanding performance when interacting with a membrane. The cost-effectiveness of membrane separation technology is considerable; therefore for more extensive membrane applications, it is critical to understand transport processes in gas membrane separations and the causes of flux decline and the capacity to anticipate flux performance. This chapter deals with mass transportation in the membrane process of gas separation. In addition, findings from many investigations carried out by a number of scholars were reviewed and discussed to study diversified facets of these complex occurrences. Investigations of diffusion pathways in the membrane pore and assessment of transport resistances caused by membrane fouling will comprehensively explain the fouling phenomena and applicable mass transfer mechanisms.

Mass transport and heat transfer in the microcirculation

Abstract: In this chapter, we develop the equations for mass transport in the microcirculation. One of the most salient molecules that is transported in the microcirculation is oxygen, and we use this molecule as our primary example. Fick’s laws of diffusion are developed and solved under these conditions. We also discuss how to model diffusion when there is a combined convection component and when kinetic reactions play a role in the diffusion. The Krogh model for tissue oxygenation is also developed. Mechanisms for the transport of other molecules such as glucose are also described, and the relationship between vascular permeability and molecular size is discussed. Energy considerations for the transport of molecules are also presented. Transport through porous media and some of the relationships necessary for this modeling are shown. Finally, methods to analyze the heat transfer under internal forced convection conditions are presented.

Hydrodynamics of charged two-dimensional Dirac systems I: thermo-electric transport

Abstract: In this paper we study thermo-electric transport in interacting two-dimensional Dirac-type systems using a phenomenological Boltzmann approach. We consider a setup that can accommodate electrons, holes, and collective modes. In the first part of the paper we consider the electron-hole hydrodynamics, a model that is popular in the context of graphene, and its transport properties. In a second part, we propose a novel type of hydrodynamics. In that setup, the `fluid' consists of electrons, holes, and plasmons. We study its transport properties, especially the thermo-electric behavior. The results of this part can also be adapted to the study of a fluid consisting of electrons and phonons. This paper is accompanied by a technical paper in which we give a detailed derivation of the Boltzmann equations and the encoded conservation laws.

Transport phenomena in fixed and fluidized-bed inorganic membrane reactors

Abstract: This chapter aims at providing a thorough (but nonexhaustive) overview on momentum, mass and heat transport occurring in fixed- and fluidized-bed inorganic membrane reactors. It discusses the mutual relationships among constitutive equations describing the complex transport phenomena determining the macroscopic performance of the considered reactors. As for the momentum transfer, several friction and drag models of literature are recalled along with the operating conditions in which they can be applied. As for the mass transport, a particular attention is paid to zeolite and metal membranes, which are the types of membrane that are used most often. As for the heat transport, several correlations for the heat transfer coefficients of literature are reported and briefly discussed.

Utilizing 3D Electrolysis Models to Link Transport to Cell Design and Performance

Abstract: Computational fluid dynamics (CFD) has been employed extensively for modeling fuel cells, but electrolysis has lacked this degree of attention in literature. As electrolysis commercialization advances, the desire to use numerical methods to aid the engineering process grows. The work described in this presentation aims to link channel/manifold geometry, porous media design, and operating conditions to cell performance in the context of mass transport and identify important unknown input quantities to which models are particularly sensitive. CFD is applied to electrolysis systems to quantify the impact of two-phase flow patterns and porous media properties on energy losses, primarily those linked directly to the presence of the gas phase. 3D models for proton exchange and alkaline electrolysis devices are summarized. For proton exchange electrolysis, a homogeneous two-phase model was built in order to estimate the species composition at the anode and how operating conditions and porous transport layer (PTL) properties influence distributions. The model suggests that cell performance is particularly sensitive to the evaporation rate and PTL permeability when the contribution of the gas-phase reaction is considered. A similar model was applied to alkaline diaphragm electrolysis to study effects of the manifolds on the flow distribution and thereby local performance. Current and gas crossover were correlated with cell geometry and altered by the cell potential and feed rate. Figure 1